The present invention relates to a reverse drive for a small vehicle and, in particular, a motorcycle.
Many small vehicles, most notably motorcycles, are commonly built without a reverse drive. This is inconvenient as it forces the operator to push the vehicle backwards out of confined spaces. A leader in reverse drive for small vehicles is the Japanese manufacturer of the HONDA brand motorcycle, which holds U.S. Pat. Nos. 4,763,538; 4,869,332; 4,870,874; and 5,024,113. All of these patents teach the use of a first internal combustion motor for a forward drive and a second electric motor for a reverse drive. By way of explanation U.S. Pat. No. 4,763,538 teaches that it is not practical to run the reverse drive off the output shaft of the internal combustion motor used for the forward drive. The reason stated is that the reduction gears required in order to provide a sufficiently slow backing speed are too large to be practical. In contrast, the HONDA references disclose how a second electric motor can be adapted for use as a reverse drive with suitably sized planetary reduction gears. The type of reverse drive disclosed in the HONDA references is not suitable for use in applications with space constraints. For example, the reverse drive disclosed in the HONDA references is not suitable for use with HARLEY-DAVIDSON brand motorcycles.
The present invention relates to an alternative configuration of reverse drive for a small vehicle.
According to the present invention there is provided a reverse drive for a small vehicle which includes a housing with a first shaft rotatably mounted in the housing. The first shaft has a first end and a second end. The first end of the first shaft extends outside the housing. A primary driven gear is mounted on the first end of the first shaft, such that an external motor engaging the primary driven gear imparts a rotary motion to the first shaft. A worm gear is mounted on and rotates with the first shaft. A second shaft is rotatably mounted in the housing. The second shaft has a first end and a second end. A worm wheel is mounted on and rotates with the second shaft. The worm wheel engages and is rotated by the worm gear with a gear reduction being effected through engagement of the worm gear and the worm wheel so that the second shaft rotates at a slower speed than the first shaft. A clutch is mounted on the second end of the second shaft. Means is provided for moving the clutch between an engaged position and a disengaged position.
The reverse drive, as described above, is comparatively compact. It uses a worm gear and worm wheel combination to effect a gear reduction. The ratio of gear reduction can be varied through the selection of the worm wheel. Although this reverse drive was developed for use on HARLEY-DAVIDSON brand motorcycles, it can be adapted for use with other small vehicles.
Although beneficial results may be obtained through the use of the invention, as described above, even more beneficial results may be obtained through the use of preferred features as are hereinafter described and claimed. It is preferred that the second shaft have two components: an outer shaft and a concentric inner shaft which is axially movable relative to the outer shaft. This concentric shaft arrangement is a compact way of mounting a movable clutch. It is preferred that a spring be used to bias the inner shaft axially to maintain the clutch in the disengaged position. This simplifies the mechanism required to move the clutch, as the clutch need only be moved in one direction to the engaged position by overcoming the biasing force of the spring. It is preferred that a lever be used to move the inner shaft axially to bring the clutch to the engaged position. The lever provides a mechanical advantage to overcome the biasing force of the spring. It is preferred that the clutch have a sawtooth engagement. The sawtooth provides a ramping effect that facilitates engagement with a corresponding sawtooth tooth clutch mounted on a remote end of a drive shaft of the small vehicle. It is preferred that movement of the lever is effected by a cable which extends from the lever to a solenoid. This enables activation of the solenoid to exert a force upon the cable to move the lever.